1. Field of the Invention
This invention relates in general to a device for indicating the depth of a hole drilled by an earth boring machine, particularly of the type utilizing a hydraulic cylinder for raising and lowering the cutting tool.
2. Description of the Prior Art
One type of machine for drilling holes for foundations, utility poles, and the like, utilizes a hydraulic cylinder for moving an auger in and out of the hole. A piston is located in the cylinder and connected to a kelly for moving the kelly longitudinally in response to hydraulic fluid pressure. An auger or other type of cutting tool is connected to the bottom of the kelly, which is rotatably driven.
Because the top of the kelly is enclosed in the cylinder, the operator is unable to determine the depth of the hole by looking at the top of the kelly. It is advantageous to know hole depth during drilling. Also, the operator has to pull the auger from the hole for every two foot or so drilled in order to spin the spoil from the auger. When returning the auger to the bottom, the auger might strike the bottom of the hole too quickly, causing damage to the machine.